Servier, an independent international pharmaceutical group governed by a foundation, has announced a definitive agreement with Kaerus Bioscience to acquire KER-0193, a potential therapy for Fragile X syndrome (FXS) — the most common genetic cause of autism spectrum disorder (ASD). This acquisition underscores Servier’s commitment to building a neurology franchise by expanding its pipeline with treatments for rare diseases where patients face significant unmet needs.
KER-0193 was discovered and developed by Kaerus Bioscience, a UK-based biotechnology company co-founded by Medicxi in 2016. In March 2025, Kaerus successfully completed a Phase 1 clinical trial in healthy volunteers, demonstrating that KER-0193 was safe, well tolerated, and showed strong pharmacokinetics. The U.S. Food and Drug Administration (FDA) has also granted KER-0193 both Orphan Drug Designation and Rare Pediatric Disease Designation for the treatment of FXS.
Under the terms of the agreement, Kaerus Bioscience will receive an upfront payment along with eligibility for development and commercial milestone-based earn-outs. The deal’s total potential value is estimated at up to $450 million.
Claude Bertrand, Executive Vice-President of R&D at Servier, said:
"KER-0193 is Servier's first asset acquisition in neurology and so marks a significant milestone in our 2030 strategy, reinforcing our long-term commitment to establishing a leading neurology franchise focused on rare diseases. It reflects our determination to build a differentiated pipeline of innovative therapies for patients with underserved needs. We are particularly excited to advance KER-0193 as we believe it holds meaningful promise for patients living with Fragile X syndrome, a condition for which no approved treatment options exist today."
Dr. Robert Ring, Chief Executive Officer of Kaerus Bioscience, said:
"We strongly believe in the therapeutic potential of KER-0193 in Fragile X syndrome. Servier's firm commitment to neurology and global capabilities make it the ideal partner to further develop KER-0193 for patients worldwide."
Michèle Ollier, Venture Partner and co-founder of Medicxi, said:
"Kaerus Bioscience was created by Medicxi to advance a clear product vision to develop a potential first-in-disease therapy for Fragile X syndrome. We are extremely proud of the cutting-edge scientific progress achieved by the Kaerus team under Dr Ring's leadership, and are excited that this deal with Servier will accelerate the development of KER-0193, bringing us closer to ensuring this innovative new therapeutic can reach those patients who are most in need."
KER-0193 is an orally bioavailable small-molecule modulator of BK channels designed to correct abnormal channel function linked to the genetic cause of FXS. Preclinical studies have shown its potential to improve behavioral, sensory, and cognitive deficits relevant to the syndrome. Servier plans to initiate a Phase 2 clinical trial in 2026 across America and Europe to further evaluate the treatment in FXS patients.
Fragile X syndrome is a rare neurodevelopmental genetic disorder associated with a spectrum of behavioral and cognitive difficulties. It is the leading single-gene cause of ASD and the most common genetic cause of intellectual disability, affecting approximately 1 in 7,000 males and 1 in 11,000 females worldwide. Currently, no approved treatments exist for FXS, which accounts for around 1% of global cases of ASD and intellectual disability.